Protecting device for electric detonators



Nov. 9 1926. 1,606,416

H. L. GRANT PROTECTING DEVICE FOR ELECTRIC DE'I'ONATORS Filed Nov. 20, 1925 Elhoentw Harry L. 67227221, 6

atented Nov. 1926.. y UNITED QFFIIE.

HARRY L. GRANT, OF TAMAQ'UA, P1LNNSYLVANIA, ASSIG-NOR TO ATLAS POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPOR-ATION OF.DELAWARE.

PROTECTING DEVICE FOR ELECTRIC DETONA'IORS.

Application filed November in wires of electric detonators and to serve,

while in position, to establish a short circuit between the two lead-in wires, so that any stray currents imposed upon the lead-1n wires, outwardly of the point of application I of said device, may not find their way .to the detonator and prematurely explode the same.

and so that no differencein potential can be created between the lead wires inwardly of the point of application of the device, under the influence of accidental or'stray currents imposed upon said wires.

I am aware of the fact that it has been proposed to short circuit the main firing cable leading from the blasting machine. However, that method is of utility only at the time of use. An important object of the present invention is to provide a structure which will be operative with respect to the individual detonators, at all times between the time of manufacture of the detonator. and until the same is actually exploded on the job, the'structure being of particular utility during the time that the detonator is being transported and while it is being handled about the work preliminary to the actual connection of its lead wires to the main firing cable. V

The present application is directed to the protection of a specific form of short circuiting shunt and method of applying-the same to the lead-in wires of the individual blasting caps, with its inner end abutting and resting firmly against the-terminal end of the usual insulation of the detonators. In the provision of a structure of this character, which is used only once and then "thrown away, it is of importance that it be of a simple and inexpensive nature and one adapted to be applied rapidly by automatic machinery. With this end in view, I have devised the shunt shown in the accompanying drawing wherein:

' Fig. 1 is a perspective view of one form of shunt prior to-its compression upon the lead wires of the detonator,

Fig. 2 is a side view of a detonator having 3 the shunt of Fig. 1 applied thereto.

20, 1925. Serial No. 70,367.

Fig. 3 is a perspective view of a-modified form of shunt prior to its application to the lead wires, and

Fig. 4 is a side view of the detonator of Fig. 3 after application to the lead wires.

Like numerals designate corresponding.

parts in all of thefigures of the drawing.

Referring to the drawing, odesignates the conventional electric detonator and 6 and 'Z designate the usual lead-in wires of said detonator.

' In the ordinary use of the detonator the flow of current of suilicient strength past an igniting element 8, which connects the inner ends of the wires (5 and 7, explodes the detonater. The lead-in wires are insulated, as indicated at 9 and l0,'for some distance from the detonator and the ends of the leadtions of the wires of the detonatonare passed through this structure and the ends ll and 11 are forced downwardly upon'the body 11 in such manner as to be firmly crimped or clamped upon the bared portions of the wires, with the insulating material abutting one edge of the shunt. The shunt is so positioned upon the lead wires as to lie obliquely with respect thereto said lead wires entering the shunt at one corner and passing therefrom at the diagonally opposed corner. An advantage of this arrangement is that the shunt presents two forwardly facing, cutting or scraping edges, one at the forward corner, or at the point marked as in Fig. 2, and the other at the point marked a, where the forward edge of the end l1 crosses the lead wires. Thus, when the shunt is removed by stripping it longitudinally from the wires, these forwardly. facing edges exert a cleaning and scraping action which cleans and brightens the lead wires and adapts them for effective electric-a1 union with the mam firing cable of a blasting machine.

The structure as illustrated in Figs. 3 and 4 is substantially like that illustrated. in Figs- 1 and 2, except that in the case of the structures of Figs. 3 and 4, the confronting edges the terms or the spirit of the appended of the bent over ends 11 and 11 are disposed upon a line that is oblique with respect to the length of the shunt but is substantially at right angles to the lead wires. This structure also possesses the advantage of presenting two forwardly facing scraping edges, which operate in the same manner as described with respect to the forms illustrated in Figs. 1 and 2. In both forms the oblique disposition of the shunt gives maximum contacting surface for a given length of shunt. It is not to be understood that the device is of utility only when actually touching the termination of the insulation. It will give a very appreciable measure of protection even when spaced somewhat from the insulation ,7 because the influences which might bring about such difference in potential between the lead wires as to explode the detonator, are not those sought to be created by an intelligent human agency but only those which might accidentally occur. Stray currents of such low E. M. F. as toescape ordinary notice constitute a marked source of danger and are rendered absolutely harmless by this' invention.

It is to be understood that the invention is not limited to the precise construction set forth but that it includes within its purview whatever changes fairly come within either claims.

Having described my invention, what I claim is:

1. The hereindescribed method of applying a short circuiting shunt to the lead wires I of an electric detonator, which consists of bending a strip of conductive material'to form a connecting body and two overturned,

inwardly directed ends, passing the bared portions of the lead wires through said structure and compressing said structure to cause it to bind firmly upon said lead wires with the shunt disposed obliquely with respect to said lead wires and with the lead wires entering at one corner of the structure and passing from said structure'at the diagonally opposed corner.

2. A shunt of the character described comprising a sheet metal element of conductive material, bent to form a connecting body portion and overturned inwardly directed ends, the confronting edges of the overturned ends being obliquely disposed with respect to the length of the shunt.

The combination with an electric detonator and its lead wires wherein said lead wires are covered for a portion of their length with an insulating material and are bare for the remainder of their length, of a shuntformed of conductive sheet metal and comprising a body portion and oppositely directed inturned ends, said shunt being clamped upon the bared portions of the wires and lying close to terminal ends of the insulation thereon, said shunt being obliquely disposed with respect to said wires, so that the wires enter the shunt at one corner thereof and leave at the diagonally opposed corner.

4. The combination with an electricdetonator and its parallel bifilar lead wires wherein said lead wires are covered with insulating material for a portion of their length and arebare for the remainder of their length, of a shunt comprising a body portion and a pair ofoverturned ends, saidshunt being clamped upon said wires close to the termination of the insulation with the body portion disposed upon one side ture.

. HARRY L. GRANT. 

